In the art of formulating agrochemicals, it is often necessary to dissolve the agrochemical active ingredient in a solvent and then dilute it in a larger volume of water in order for it to be broadcast in the form of a fine spray. In still other cases, it is necessary to dilute the active ingredient in a solution and apply it to a seed or other solid carrier. While some active ingredients, which are usually in the form of a salt, can be simply dissolved and then diluted in water, the majority of agrochemical active ingredients are hydrophobic and therefore not water-soluble. In the case of active ingredients which are not water-soluble, it is normally necessary to dissolve the formulation in a water-immiscible solvent and add surfactants, so that the solution will form an oil-in-water emulsion when added to water. Such a formulation is called an Emulsifiable Concentrate (EC) formulation. Alternatively, the water-immiscible solution of an active ingredient can be pre-emulsified in water in a concentrated form. Such a formulation is called an Emulsion-in-Water (EW) formulation. A special sub-class of EW formulations is the so-called Microemulsion (ME) formulation, where the emulsion particle size is such that the formulation does not scatter light and has a clear or translucent appearance.
Water-immiscible solvents commonly used for EC and EW formulations include, but are not limited to, aromatic hydrocarbons such as the SOLVESSO® series, paraffinic hydrocarbons such as the EXXSOL® range, ester solvents such as the EXXATE© range, all of which are manufactured by EXXONMOBIL, and ester solvents such as methyloleate. Other solvents which are water-immiscible at high concentration include cyclic hydrocarbons, such as cyclohexanone and isophorone.
In more recent times, solvents which exhibit improved toxicity and reduced flammability profiles have been used. These include the dibasic ester solvents of long chain di-acids having from 8-16 carbon units, which are usually methyl ester derivatives, and fatty acid amide solvents, examples of which are the dimethylamide and morpholineamide derivatives of C6-C16 fatty acids. Mono-alkylene carbonates, such as ethylene, propylene and butylene carbonates, also find use as co-solvents, although they can generally be considered as water-miscible when used at most practical end-use dilution rates.
Combinations of water-immiscible solvents with highly polar water-miscible co-solvents such as N-methyl pyrrolidinone, dimethylsulphoxide, dimethylisosorbide, monoethylene glycol, monopropylene glycol and various glycol ethers, have been used in the past to achieve physical stability of the EC formulation, particularly if crystallisation of the active ingredient occurs at below ambient temperature. However, the use of such solvent combinations often leads to the problem of crystallisation in the diluted formulation.
There is a particular need for low toxicity and low flammability polar solvents, which can dissolve the more polar active ingredients, but which are not so polar as to have significant water-solubility resulting in crystallisation of the active ingredient upon dilution. In particular, it is desirable to be able to dissolve certain problematic agrochemical active ingredients in high concentration for use in emulsifiable concentrate formulations. High concentration EC formulations have significant advantages in costs, shipping and handling. Such active ingredients include, but are not limited to, dinitroaniline herbicides such as trifluralin, pendimethalin, benfluralin and butralin; diphenylether herbicides such as oxyfluorfen and aclonifen; phenoxypropionate herbicides such as metamifop; synthetic pyrethroid insecticides such as deltamethrin, bifenthrin, zeta-cypermethrin, gamma- and lambda-cyhalothrin and alpha-cypermethrin; organophosphate insecticides such as phosmet and omethoate; and various acaricides including amitraz, buprofezin and pyridaben.
While many of the dibasic ester and fatty amide-based solvents can dissolve some of the active ingredients in the polarity range of these solvents, there are limitations on the amount of active ingredient that can be dissolved. Further, not all of these classes of solvents have desirable toxicity profiles. In addition, significant effort and expense can be involved in the manufacture and, in particular, the purification of these solvents.
While mono-short chain alkylene carbonate solvents have an overall excellent toxicity profile and reduced flammability, their major limitation is that they are generally water-miscible upon dilution and do not fully dissolve many of the active ingredients described above.
The use of benzyl acetate as a solvent for agrochemical active ingredients is known. Japanese Patent Application JP 2009173569A teaches the use of benzyl acetate and butylacetoacetate in combination with a water-miscible co-solvent, 1,3-dimethyl-2-imidazolidinone and an aromatic hydrocarbon to prepare emulsion compositions of various hydrophobic agrochemical active ingredients up to 50% weight/volume. International Patent Publication No. WO 2011/017480 teaches benzyl acetate as a suitable solvent for dissolving certain active ingredients in preparation for forming microcapsule compositions.
There is, however, still a need for water-immiscible solvent combinations, having an improved toxicity and flammability profile.
The present invention seeks to provide an improved solvent system for high concentration emulsifiable concentrate formulations that at least ameliorates certain disadvantages associated with previously known solvent systems.